A self-unplugging carbonate reservoir drilling fluid

Abstract

The invention discloses a self-plugging removal carbonate reservoir drill-in fluid. The self-plugging removal carbonate reservoir drill-in fluid comprises the following components in parts by weight: 100 parts of water, 5-16 parts of compound type self-plugging removal temporary plugging agent, 2-6 parts of fluid loss additive, 0.1-0.8 part of tackifier, 0.1-0.5 part of pH regulator, 0.1-0.5 part of waterproof locking agent, 0-7 parts of potassium chloride and 0-230 parts of weighting agent, wherein the addition amount of the weighting agent is greater than zero. The self-plugging removal carbonate reservoir drill-in fluid disclosed by the invention is reasonable in rheological property, can meet the rheological property requirements of drilling reservoirs of vertical shafts, directional wells and horizontal wells and has good fluid loss well building property. The self-plugging removal carbonate reservoir drill-in fluid has strong capacity of resisting pollution of acid gas such as H2S and CO2, excellent reservoir protection performance and good compatibility with a formation fluid, and the carbonate rock core return permeability of the self-plugging removal carbonate reservoir drill-in fluid is greater than 87%; and a gel breaker is not needed, and the self-plugging removal carbonate reservoir drill-in fluid can be used for direct plugging removal through acid pickling and putting into production.

Description

technical field [0001] The invention relates to a drilling fluid, in particular to a drilling fluid for self-blocking carbonate rock reservoirs. Background technique [0002] Carbonate rock is an extremely important oil and gas reservoir. According to statistics, the oil and gas production of carbonate rock reservoirs in the world accounts for about 60% of the total oil and gas production. The lithology of this type of reservoir is mainly limestone and dolomite, with good storage properties. There are extremely rich carbonate rock reservoirs in the Middle East, North America, Siberia, as well as the Tarim Basin, Sichuan Basin and North China Plain in my country. Of great value to the petroleum industry. The key technical problems faced by the drilling of carbonate reservoirs include: (1) Carbonate reservoirs are highly heterogeneous, with well-developed reservoir holes and fractures, and the opening of fractures is uncertain, leading to serious leakage problems. ②Due to the...

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Problems solved by technology

The key technical problems faced by drilling carbonate reservoirs include: ① Carbonate reservoirs are highly heterogeneous, reservoirs have well-developed pores and fractures, and the opening of fractures is uncertain, leading to serious leakage problems

②Due to the development of fractures, carbonate reservoirs are extremely vulnerable to external fluid and solid phase damage, including the incompatibility between the drilling fluid filtrate and formation water that invaded the formation, and the physical and chemical interaction between the drilling fluid filtrate and formation minerals to produce precipitation, resulting in reservoir seepage Reservoir damage caused by the intrusion of solid particles in the drilling fluid into the formation, and oil and gas seepage resistance caused by water locking in micro-fractures, etc., will all lead to a decline in productivity

③The content of acid gas hydrogen sulfide and carbon dioxide in the formation is high. The existence of hydrogen sulfide not only poses a safety hazard, but also has a negative impact on the performance of the drilling fluid, and at the same time aggravates the corrosion of drilling tools

④The formation strength is low, and generally contains salt-gypsum or mudstone interlayers, and there are problems of borehole wall collapse and tripping jamming

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